U.S. patent application number 16/546467 was filed with the patent office on 2019-12-12 for graphene modified iron-based catalyst and preparation and application thereof for use in fischer-tropsch reaction.
The applicant listed for this patent is Jiangnan University. Invention is credited to Feng JIANG, Bing LIU, Xiaohao LIU, Yuebing XU.
Application Number | 20190374928 16/546467 |
Document ID | / |
Family ID | 59603936 |
Filed Date | 2019-12-12 |
United States Patent
Application |
20190374928 |
Kind Code |
A1 |
LIU; Xiaohao ; et
al. |
December 12, 2019 |
Graphene Modified Iron-Based Catalyst and Preparation and
Application Thereof for Use in Fischer-Tropsch Reaction
Abstract
The present disclosure disclosures a graphene modified
iron-based catalyst and preparation and application thereof for use
in Fischer-Tropsch reaction, belonging to the technical field of
catalytic conversion of synthesis gas. The catalyst consists of, by
mass percent, 0.01-30% of graphene, 0-20% of promoter and 60-99.99%
of iron oxide powder. The preparation process of the catalyst is as
follows: the graphene, the iron oxide powder and the promoter are
sequentially placed in an aqueous solution for ultrasonic treatment
and stirring, and then rotary evaporation, drying and calcining are
conducted. The preparation method is simple. The catalyst shows
excellent activity in the Fischer-Tropsch reaction, and maintains a
high CO conversion rate of 90% or above for a long time at a very
high reaction space velocity; meanwhile, the alkane content in a
product is low, and an olefin-alkane ratio can reach 14, thus
having an extremely high industrial application value.
Inventors: |
LIU; Xiaohao; (Wuxi, CN)
; XU; Yuebing; (Wuxi, CN) ; JIANG; Feng;
(Wuxi, CN) ; LIU; Bing; (Wuxi, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Jiangnan University |
Wuxi |
|
CN |
|
|
Family ID: |
59603936 |
Appl. No.: |
16/546467 |
Filed: |
August 21, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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PCT/CN2017/119418 |
Dec 28, 2017 |
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16546467 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B01J 23/80 20130101;
B01J 37/08 20130101; B01J 37/009 20130101; B01J 37/088 20130101;
C10G 2300/70 20130101; B01J 37/0036 20130101; B01J 37/343 20130101;
B01J 23/78 20130101; C10G 2/332 20130101; B01J 23/8892 20130101;
B01J 35/0013 20130101; B01J 23/745 20130101; C10G 2/344 20130101;
B01J 21/18 20130101; B01J 23/881 20130101; B01J 37/0238 20130101;
B01J 37/0027 20130101 |
International
Class: |
B01J 23/745 20060101
B01J023/745; B01J 37/34 20060101 B01J037/34; B01J 37/08 20060101
B01J037/08; C10G 2/00 20060101 C10G002/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 2, 2017 |
CN |
2017103004722 |
Claims
1. A method for preparing a graphene modified iron-based catalyst,
wherein raw materials comprise 0.01-30 parts by mass of graphene,
0-20 parts by mass of promoter and 60-99.99 parts by mass of iron
oxide, the method comprising the following steps: (1) dispersing
the graphene in an aqueous solution at 10-80.degree. C. to form a
suspension, ultrasonically dispersing for 0.5-5 h, and then
stirring for 1-24 h; (2) adding the iron oxide into the suspension
formed in the step (1) according to a stoichiometric ratio, and
continuously stirring for 0.5-24 h; (3) adding a precursor of the
promoter into the suspension formed in the step (2) according to a
stoichiometric ratio, and continuously stirring for 1-24 h; and (4)
conducting rotary evaporation on a solution obtained in the step
(3) to dryness, drying an obtained solid at 80-120.degree. C. for
1-24 h, and then calcining in a gas of nitrogen, helium or argon at
250-800.degree. C. for 1-24 h to obtain the graphene modified
iron-based catalyst, and wherein when the promoter is 0 part by
mass, the step (3) is omitted.
2. The method according to claim 1, wherein the precursor is
selected from soluble compounds containing promoter elements.
3. The method according to claim 2, wherein the precursor is one
selected from a group consisting of nitrate, carbonate, acetate,
molybdate, sulfide, and any combination thereof.
4. The method according to claim 1, wherein the iron oxide is one
selected from a group consisting of ferroferric oxide, ferric
oxide, ferrous oxide, and any combination thereof; and the iron
oxide has a particle size of 50-1000 nm.
5. The method according to claim 4, wherein the particle size is
100-500 nm.
6. The method according to claim 1, wherein the promoter is one
selected from a group consisting of K, Na, Mn, Cu, Zn, Mo, Co, S,
and any combination thereof.
7. The method according to claim 3, wherein the promoter is one
selected from a group consisting of K, Na, Mn, Cu, Zn, Mo, Co and
S, and any combination thereof.
8. A graphene modified iron-based catalyst prepared by the method
according to claim 1.
9. A method of conducting Fischer-Tropsch reaction by using the
graphene modified iron-based catalyst according to claim 8,
comprising applying the catalyst to catalyze the Fischer-Tropsch
reaction of synthesis gas, wherein the catalyst is pre-reduced with
H.sub.2 for a certain period of time before the reaction, and then
the catalyst is cooled to a reaction temperature to perform
catalytic reaction.
10. The method according to claim 9, the further comprising
pressing the catalyst at a pressure of 5.5 MPa, crushing the
catalyst, and sieving the catalyst through a 40-60 mesh sieve.
11. The method according to claim 9, wherein the catalyst is placed
in a continuous flow reactor to catalyze continuous reaction.
12. The method according to claim 10, wherein the catalyst is
placed in a continuous flow reactor to catalyze continuous
reaction.
Description
TECHNICAL FIELD
[0001] The disclosure herein relates to a graphene modified
iron-based catalyst and preparation and application thereof for use
in Fischer-Tropsch reaction, belonging to the technical field of
catalytic conversion of synthesis gas.
BACKGROUND
[0002] Lower olefins, including ethylene, propylene and butylene,
are important chemical raw materials, which mainly derive from the
cracking of naphtha. With the decrease of crude oil resources, the
increasingly prominent environmental problems, and the scale
development of shale gas, obtaining olefins from petroleum is
challenged and becomes unsustainable. Therefore, more and more
attention has been paid to the preparation of lower olefins by
non-petroleum routes. Direct production of lower olefins from
synthesis gas, serving as an alternative technology route for the
production of lower olefins such as ethylene and propylene, is of
great significance for the utilization of China's abundant coal
resources and the alleviation of dependence on petroleum resources.
The process does not need to prepare olefins from synthesis gas
through methanol or dimethyl ether like an indirect process, so
that the process flow is simplified, operation cost is low and
investment is greatly reduced.
[0003] Direct production of lower olefins from synthesis gas refers
to a process in which synthesis gas (CO and H.sub.2) is used for
producing olefins with the number of carbon atoms less than or
equal to 4 through Fischer-Tropsch synthesis under the action of a
catalyst. The process produces water and CO.sub.2 as by-products.
As the distribution of Fischer-Tropsch synthesis products is
limited by the Anderson-Schulz-Flory law (the molar distribution of
chain growth decreasing exponentially), and the strong
exothermicity of the reaction easily leads to the generation of
methane and lower alkanes, and promotes the secondary reaction of
generated olefins, it is difficult to obtain lower olefins with
high selectivity, and the key lies in the development of
high-performance catalysts.
[0004] Although there are literature reports about using a
cobalt-based or ruthenium-based catalyst for Fischer-Tropsch
reaction to produce lower olefins, an iron-based catalyst has
become the preferred active component for Fischer-Tropsch synthesis
to directly produce lower olefins due to the low cost and high
lower olefin selectivity. Recently, it is often reported in the
literature that carbon materials are used in the preparation of the
iron-based catalyst. The carbon materials can not only provide the
required stability, but also facilitate the reduction and
activation of iron species. Therefore, the carbon materials have
become a research hotspot in recent years whether as supports or
promoters. Graphene, as a new type of carbon material, has the
advantages of large specific surface area, unique two-dimensional
structure, excellent electrical and thermal conductivity, and easy
chemical modification, and is considered to be an ideal catalyst
support or promoter. However, in most of the current researches,
graphene is added to an iron-based catalyst precursor, the
preparation process is complex, and the improvement in catalytic
performance and stability is not quite significant. Therefore, it
is necessary to develop a method which can directly modify the
iron-based catalyst with graphene, so as to simplify the
preparation process of the catalyst, and improve the activity of
the catalyst, lower olefin selectivity and stability at the same
time.
SUMMARY
[0005] The present disclosure relates to a graphene modified
iron-based catalyst capable of realizing the preparation of lower
olefins with high selectivity from synthesis gas, and capable of
preparing higher .alpha.-olefin with high activity, good stability
and a simple preparation method, as well as a preparation method
thereof.
[0006] The catalyst according to the present disclosure is a
graphene modified iron-based catalyst, and application of the
graphene modified iron-based catalyst in Fischer-Tropsch reaction
is also provided.
[0007] The graphene modified iron-based catalyst includes, in parts
by mass, 0.01-30 parts of graphene, 0-20 parts of promoter and
60-99.99 parts of iron oxide powder.
[0008] In one embodiment of the present disclosure, the iron oxide
is one or any combination of ferroferric oxide, ferric oxide and
ferrous oxide, and a particle size of the iron oxide is 50-1000 nm,
preferably 100-500 nm.
[0009] In one embodiment of the present disclosure, the promoter is
one or any combination of K, Na, Mn, Cu, Zn, Mo, Co and S.
[0010] The present disclosure further provides a method for
preparing the graphene modified iron-based catalyst, including the
following steps:
[0011] (1) dispersing the graphene in an aqueous solution at
10-80.degree. C. to form a suspension, ultrasonically dispersing
for 0.5-5 h, and then stirring for 1-24 h;
[0012] (2) adding the iron oxide into the suspension formed in the
step (1) according to a stoichiometric ratio, and continuously
stirring for 0.5-24 h;
[0013] (3) adding an promoter precursor into the suspension formed
in the step (2) according to a stoichiometric ratio, and
continuously stirring for 1-24 h; and
[0014] (4) conducting rotary evaporation on a solution obtained in
the step (3) to dryness, drying an obtained solid at 80-120.degree.
C. for 1-24 h, and then calcining in a gas of nitrogen, helium or
argon at 250-800.degree. C. for 1-24 h to obtain the graphene
modified iron-based catalyst; and when the content of the promoter
is 0 part, the step (3) is omitted.
[0015] In one embodiment of the present disclosure, the promoter
precursor is selected from soluble compounds containing promoter
elements, and preferably is one or more of nitrate, carbonate,
acetate, molybdate and sulfide.
[0016] The present disclosure further provides a method for
preparing synthesis gas from the prepared graphene modified
iron-based catalyst, the catalyst is pre-reduced with H.sub.2 for a
certain period of time before reaction, and then the catalyst is
cooled to a reaction temperature for catalytic reaction.
[0017] In one embodiment of the present disclosure, the graphene
modified iron-based catalyst is pressed at a pressure of 5.5 MPa,
crushed, sieved through a 40-60 mesh sieve and then used for the
Fischer-Tropsch reaction.
[0018] In one embodiment of the present disclosure, the graphene
modified iron-based catalyst is placed in a continuous flow reactor
to catalyze continuous reaction.
[0019] Compared with the prior art, the present disclosure has the
following advantages that:
[0020] (1) the prepared catalyst has a simple preparation method
and is prepared with only a few steps; a small sized iron carbide
active phase which can be effectively formed in the reaction
process maintains a high activity; especially in the
Fischer-Tropsch reaction, an excellent activity is shown, and a
high CO conversion rate of 90% or above is maintained for a long
time at a very high reaction space velocity; meanwhile, the alkane
content in a product is low, and an olefin-alkane ratio can reach
14, thus having an extremely high industrial application value;
and
[0021] (2) the prepared catalyst has extremely high total olefin
selectivity and low methane selectivity; the activity of the
catalyst is extremely high, and the stability of the catalyst can
be maintained at an extremely high space velocity.
BRIEF DESCRIPTION OF FIGURES
[0022] FIG. 1 is an SEM image of ferric oxide powder in Examples 1
and 2.
[0023] FIG. 2 is an SEM image of ferroferric oxide powder in
Examples 3 and 4.
[0024] FIG. 3 is an SEM image of ferroferric oxide powder in
Example 5.
DETAILED DESCRIPTION
[0025] Definition and calculation formula of conversion rate:
X CO ( % ) = [ CO ] i n - [ CO ] out [ CO ] i n .times. 100 % ,
##EQU00001##
[0026] wherein [CO].sub.in represents the molar concentration of CO
in inlet gas of a reactor, and [CO].sub.out represents the molar
concentration of CO in outlet gas of the reactor.
[0027] Definition and calculation formula of selectivity:
S CH 4 ( % ) = [ CH 4 ] out [ CO ] i n - [ CO ] out .times. 100 % ,
##EQU00002##
[0028] wherein [CO].sub.out represents the molar concentration of
CO.sub.2 in the outlet gas of the reactor, and [CH.sub.4].sub.out
represents the molar concentration of CH.sub.4 in the outlet gas of
the reactor.
[0029] Selectivity S.sub.Cn of hydrocarbons with a carbon number of
n in products, and selectivity S.sub.Cn-n+k of hydrocarbons with
carbon numbers ranging from n to n+k in the products:
S Cn ( % ) = [ Cn ] out [ CH 4 ] out .times. S CH 4 , S Cn - n + k
( % ) = i = n i = n + k S Ci , ##EQU00003##
[0030] wherein [Cn].sub.out represents the molar concentration of
hydrocarbons with a carbon number of n in the outlet gas of the
reactor.
Examples 1-4 Preparation of Graphene Modified Iron-Based
Catalyst
Example 1
[0031] 0.677 g graphene oxide and 3.112 g ferric oxide powder were
respectively taken, dispersed in an aqueous solution at 40.degree.
C. in sequence, and continuously stirred for 12 h; then rotary
evaporation to dryness at 85.degree. C. and dry at 105.degree. C.
for 24 h were conducted; and then calcined at 400.degree. C. for 5
h in a nitrogen atmosphere to obtain a catalyst A with a graphene
content of 17.8% and a ferric oxide content of 82.2%, wherein the
average particle diameter of ferric oxide in the catalyst was 120
nm, as shown in FIG. 1.
Example 2
[0032] 0.325 g graphene oxide, 2.876 g ferric oxide powder and
0.0715 g potassium carbonate were respectively taken, dispersed and
dissolved in an aqueous solution at 40.degree. C. in sequence, and
continuously stirred for 12 h; then rotary evaporation to dryness
at 85.degree. C. and dry at 105.degree. C. for 24 h were conducted;
and then calcined at 400.degree. C. for 5 h in a nitrogen
atmosphere to obtain a catalyst B with a graphene content of 10%, a
ferric oxide content of 88.5%, and a potassium oxide content of
1.5%, wherein the average particle diameter of ferric oxide in the
catalyst was 120 nm, as shown in FIG. 1.
Example 3
[0033] 0.551 g graphene oxide and 4.052 g ferroferric oxide powder
were respectively taken, dispersed in an aqueous solution at
40.degree. C. in sequence, and continuously stirred for 12 h; then
rotary evaporation to dryness at 85.degree. C. and dry at
105.degree. C. for 24 h were conducted; and then calcined at
400.degree. C. for 5 h in a nitrogen atmosphere to obtain a
catalyst C with a graphene content of 12% and a ferroferric oxide
content of 88%, wherein the average particle diameter of
ferroferric oxide in the catalyst was 290 nm, as shown in FIG.
2.
Example 4
[0034] 0.861 g graphene oxide, 4.001 g ferroferric oxide powder,
and 0.435 g potassium nitrate were respectively taken, dispersed
and dissolved in an aqueous solution at 40.degree. C. in sequence,
and continuously stirred for 12 h; then rotary evaporation to
dryness at 85.degree. C. and dry at 105.degree. C. for 24 h were
conducted; and then calcined at 400.degree. C. for 5 h in a
nitrogen atmosphere to obtain a catalyst D with a graphene content
of 17%, a ferroferric oxide content of 79%, and a potassium oxide
content of 4%, wherein the average particle diameter of ferroferric
oxide in the catalyst was 290 nm, as shown in FIG. 2.
Example 5
[0035] 0.861 g graphene oxide, 4.001 g ferroferric oxide powder,
and 0.435 g potassium nitrate were respectively taken, dispersed
and dissolved in an aqueous solution at 40.degree. C. in sequence,
and continuously stirred for 12 h; then rotary evaporation to
dryness at 85.degree. C. and dry at 105.degree. C. for 24 h were
conducted; and then calcined at 400.degree. C. for 5 h in a
nitrogen atmosphere to obtain a catalyst G with a graphene content
of 17%, a ferroferric oxide content of 79%, and a potassium oxide
content of 4%, wherein the average particle diameter of ferroferric
oxide in the catalyst was 610 nm, as shown in FIG. 3.
Example 6
[0036] 0.677 g graphene oxide and 3.112 g ferric oxide powder were
respectively taken, dispersed in an aqueous solution at 40.degree.
C. in sequence, and continuously stirred for 5 h; then rotary
evaporation to dryness at 85.degree. C. and dry at 120.degree. C.
for 12 h were conducted; and then calcined at 600.degree. C. for 3
h in a nitrogen atmosphere to obtain a catalyst H with a graphene
content of 17.8% and a ferric oxide content of 82.2%, wherein the
average particle diameter of ferric oxide in the catalyst was 120
nm.
Examples 7-10 Application of Graphene Modified Iron-Based Catalyst
in Synthesis Gas Conversion
[0037] A prepared catalyst was pressed at a pressure of 5.5 MPa,
crushed and sieved to obtain a 40-60 mesh sample; and 0.15 g
catalyst was taken and placed in a continuous flow reactor, the
catalyst was pre-reduced with H.sub.2 for a certain period of time
before reaction, and then cooled to a reaction temperature to
perform continuous reaction. The reaction gas was composed of 47.5
vol % CO, 47.5 vol % H.sub.2 and 5 vol % Ar, wherein Ar was used as
the internal standard gas to calculate the conversion rate of CO.
The products were analyzed on-line at atmospheric pressure after
being cooled in a cold trap by a gas chromatography equipped with
TCD and FID detectors.
Example 7
[0038] The catalysts A, G and H were placed in a pressurized fixed
bed reactor, heated to 380.degree. C. at a rate of 5.degree. C./min
in an H.sub.2 atmosphere, and reduced for 10 h at atmospheric
pressure and a space velocity of 1000 h.sup.-1; and then the
temperature was reduced, and reaction gases were introduced for
reaction at a reaction pressure of 1.0 MPa, a reaction space
velocity of 20000 h.sup.-1, and reaction temperatures of
300.degree. C., 320.degree. C. and 340.degree. C., so as to
investigate the influence of the reaction temperatures. The results
of the conversion rate of CO and olefin selectivity are shown in
Table 1.
Example 8
[0039] The catalyst B was placed in a pressurized fixed bed
reactor, heated to 380.degree. C. at a rate of 5.degree. C./min in
an H.sub.2 atmosphere, and reduced for 10 h at atmospheric pressure
and a space velocity of 1000 h.sup.-1; and then the temperature was
reduced, and reaction gases were introduced for reaction at a
reaction pressure of 1.0 MPa, a reaction temperature of 300.degree.
C., and reaction space velocities of 10000 h.sup.-1, 20000 h.sup.-1
and 40000 h.sup.-1, so as to investigate the influence of the
reaction space velocities. The results of the conversion rate of CO
and olefin selectivity are shown in Table 1.
Example 9
[0040] The catalyst C was placed in a pressurized fixed bed
reactor, heated to 380.degree. C. at a rate of 5.degree. C./min in
an H.sub.2 atmosphere, and reduced for 10 h at atmospheric pressure
and a space velocity of 1000 h.sup.-1; and then the temperature was
reduced, and reaction gases were introduced for reaction at a
reaction pressure of 1.0 MPa, a reaction space velocity of 20000
h.sup.-1, and a reaction temperature of 340.degree. C. The results
of the conversion rate of CO and olefin selectivity are shown in
Table 1.
Example 10
[0041] The catalyst D was placed in a pressurized fixed bed
reactor, a fluidized bed reactor and a slurry bed reactor
respectively, heated to 380.degree. C. at a rate of 5.degree.
C./min in an H.sub.2 atmosphere, and reduced for 10 h at
atmospheric pressure and a space velocity of 1000 h.sup.-1; and
then the temperature was reduced, and reaction gases were
introduced for reaction at a reaction pressure of 1.0 MPa, a
reaction space velocity of 20000 h.sup.-', and a reaction
temperature of 340.degree. C. The results of the conversion rate of
CO and olefin selectivity are shown in Table 1. This result was
used to compare the reaction results of the catalyst in different
reactors.
Comparative Example 1
[0042] 3.88 g ferric oxide powder and 0.176 g potassium carbonate
were respectively taken, dispersed and dissolved in an aqueous
solution at 40.degree. C. in sequence, and continuously stirred for
12 h; then rotary evaporation to dryness at 85.degree. C. and dry
at 105.degree. C. for 24 h were conducted; and then calcined at
400.degree. C. for 5 h in a nitrogen atmosphere to obtain a
catalyst E with a ferric oxide content of 97% and a potassium oxide
content of 3%, wherein the average particle diameter of ferric
oxide in the catalyst was 120 nm, as shown in FIG. 1. The catalyst
was placed in a pressurized fixed bed reactor, heated to
380.degree. C. at a rate of 5.degree. C./min in an H.sub.2
atmosphere, and reduced for 10 h at atmospheric pressure and a
space velocity of 1000 h.sup.-1; and then the temperature was
reduced, and reaction gases were introduced for reaction at a
reaction pressure of 1.0 MPa, a reaction space velocity of 20000
h.sup.-', and reaction temperatures of 300.degree. C. and
340.degree. C., so as to investigate the influence of the reaction
temperatures. The results of the conversion rate of CO and olefin
selectivity are shown in Table 2.
Comparative Example 2
[0043] 0.506 g activated carbon, 4.948 ferroferric oxide powder and
0.248 g potassium carbonate were respectively taken, dispersed and
dissolved in an aqueous solution at 40.degree. C. in sequence, and
continuously stirred for 12 h; then rotary evaporation to dryness
at 85.degree. C. and dry at 105.degree. C. for 24 h were conducted;
and then calcined at 400.degree. C. for 5 h in a nitrogen
atmosphere to obtain a catalyst F with an activated carbon content
of 9%, a ferroferric oxide content of 89% and a potassium oxide
content of 3%, wherein the average particle diameter of ferroferric
oxide in the catalyst was 290 nm, as shown in FIG. 2. The catalyst
was placed in a pressurized fixed bed reactor and a fluidized bed
reactor, heated to 380.degree. C. at a rate of 5.degree. C./min in
an H.sub.2 atmosphere, and reduced for 10 h at atmospheric pressure
and a space velocity of 1000 h.sup.-1; and then the temperature was
reduced, and reaction gases were introduced for reaction at a
reaction pressure of 1.0 MPa, a reaction space velocity of 20000
h.sup.-1, and a reaction temperature of 340.degree. C. The results
of the conversion rate of CO and olefin selectivity are shown in
Table 2.
Comparative Example 3
[0044] 0.677 g graphene oxide and 15.716 g iron nitrate nonahydrate
were respectively taken, dispersed in an aqueous solution at
40.degree. C. in sequence, and continuously stirred for 12 h; then
rotary evaporation to dryness at 85.degree. C. and dry at
105.degree. C. for 24 h were conducted; and then calcined at
400.degree. C. for 5 h in a nitrogen atmosphere to obtain a
catalyst I with a graphene content of 17.8% and a ferric oxide
content of 82.2%. The catalyst was placed in a pressurized fixed
bed reactor, heated to 380.degree. C. at a rate of 5.degree. C./min
in an H.sub.2 atmosphere, and reduced for 10 h at atmospheric
pressure and a space velocity of 1000 h.sup.-1; and then the
temperature was reduced, and reaction gases were introduced for
reaction at a reaction pressure of 1.0 MPa, a reaction space
velocity of 20000 h.sup.-1, and a reaction temperature of
340.degree. C. The results of the conversion rate of CO and olefin
selectivity are shown in Table 2.
Comparative Example 4
[0045] 2.568 g graphene oxide and 3.112 g ferric oxide powder were
respectively taken, dispersed in an aqueous solution at 40.degree.
C. in sequence, and continuously stirred for 12 h; then rotary
evaporation to dryness at 85.degree. C. and dry at 105.degree. C.
for 24 h were conducted; and then calcined at 400.degree. C. for 5
h in a nitrogen atmosphere to obtain a catalyst J with a graphene
content of 45.2% and a ferric oxide content of 54.8%, wherein the
average particle diameter of ferric oxide in the catalyst was 120
nm, the same as that in Example 1. The catalyst was placed in a
pressurized fixed bed reactor, heated to 380.degree. C. at a rate
of 5.degree. C./min in an H.sub.2 atmosphere, and reduced for 10 h
at atmospheric pressure and a space velocity of 1000 h.sup.-1; and
then the temperature was reduced, and reaction gases were
introduced for reaction at a reaction pressure of 1.0 MPa, a
reaction space velocity of 20000 h.sup.-1, and a reaction
temperature of 340.degree. C. The results of the conversion rate of
CO and olefin selectivity are shown in Table 2.
Comparative Example 5
[0046] 0.677 g graphene oxide and 3.112 g ferric oxide powder were
respectively taken, dispersed in an aqueous solution at 40.degree.
C. in sequence, and continuously stirred for 12 h; then rotary
evaporation to dryness at 85.degree. C. and dry at 105.degree. C.
for 24 h were conducted; and then calcined at 400.degree. C. for 5
h in a nitrogen atmosphere to obtain a catalyst K with a graphene
content of 17.8% and a ferric oxide content of 82.2%, wherein the
average particle diameter of ferric oxide in the catalyst was 10
nm. The catalyst was placed in a pressurized fixed bed reactor,
heated to 380.degree. C. at a rate of 5.degree. C./min in an
H.sub.2 atmosphere, and reduced for 10 h at atmospheric pressure
and a space velocity of 1000 h.sup.-1; and then the temperature was
reduced, and reaction gases were introduced for reaction at a
reaction pressure of 1.0 MPa, a reaction space velocity of 20000
h.sup.-1, and a reaction temperature of 340.degree. C. The results
of the conversion rate of CO and olefin selectivity are shown in
Table 2.
TABLE-US-00001 TABLE 1 Reaction Performance of Different Catalysts
in Preparing Lower Olefins through Synthesis Gas Conversion
Hydrocarbon product Reaction Reaction Conversion distribution
temperature space rate of CO (C-mol %) Olefin-alkane Catalyst
(.degree. C.) velocity (h.sup.-1) (%) CH.sub.4 C.sub.2+.sup.=
C.sub.2+.sup.0 ratio (O/P) A 300 20000 65.2 9.7 83.4 6.9 12.1 A 320
20000 78.5 11.2 81.0 7.8 10.4 A 340 20000 90.2 13.8 79.0 7.2 10.9 B
320 10000 85.1 12.1 81.9 6.0 13.6 B 320 20000 79.2 11.2 82.7 6.1
13.5 B 320 40000 70.4 11.7 82.0 6.3 13.0 C 340 20000 92.1 14.2 80.0
5.8 13.7 D 340 20000 93.2 12.7 80.8 6.5 12.4 D* 340 20000 92.9 10.5
83.5 6.0 14.0 D** 340 20000 90.8 9.8 83.7 6.5 12.9 G 340 20000 80.3
11.8 76.6 11.6 6.6 H 340 20000 87.5 11.6 82.4 6.0 13.7 Reaction
conditions: fixed bed reactor, 1.0 MPa, average data within 100-500
h of reaction. *Fluidized bed reactor; **Slurry bed reactor
TABLE-US-00002 TABLE 2 Experimental Results of Comparative Examples
Hydrocarbon product distribution Reaction Reaction space Conversion
(C-mol %) Olefin alkane Catalyst temperature (.degree. C.) velocity
(h.sup.-1) rate of CO (%) CH.sub.4 C.sub.2+.sup.= C.sub.2+.sup.0
ratio (O/P) E 300 20000 12.3 34.5 24.6 40.9 0.6 E 340 20000 5.6
41.2 19.6 39.2 0.5 F 320 20000 8.9 37.7 25.7 36.6 0.7 F* 320 20000
11.1 32.9 25.2 41.9 0.6 I 340 20000 20.6 40.5 20.7 38.8 0.5 J 340
20000 1.2 60.7 6.8 32.5 0.2 K 340 20000 89.6 20.5 14.3 65.2 0.2
Reaction conditions: fixed bed reactor, 1.0 MPa, average data
within 5-10 h. *Fluidized bed reactor
[0047] Comparing the experimental results in Table 1 and Table 2,
it can be clearly seen that the graphene modified iron-based
catalyst exhibits excellent catalytic performance, maintains a
stable activity within 500 h of reaction, and still exhibits a very
high CO conversion rate at a very high reaction space velocity.
Even in the absence of promoter, olefin selectivity in the products
is close to 50%, and olefin-alkane ratio can reach 13. However,
iron-based catalysts without graphene modification or modified with
other carbon materials quickly lose the activity within a few hours
of reaction, and the products are mainly alkanes. The results show
that the graphene modified iron-based catalyst has an excellent
industrial application value.
[0048] Although the present disclosure has been disclosed in terms
of preferred examples, the preferred examples are not intended to
limit the present disclosure. Any person familiar with this
technology can make various changes and modifications without
departing from the spirit and scope of the present disclosure.
Therefore, the scope of protection of the present disclosure should
be as defined in the claims.
* * * * *